Forming Ions - Ionic Compounds - AQA Trilogy - BBC Bitesize - BBC

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2. Video
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Pages

1. Forming ions
2. Forming ionic bonds
3. The ionic lattice
4. Properties of ionic compounds

Forming ions

An ion is an atom or group of atoms with a positive or negative charge. Ions form when atoms lose or gain electrons to obtain a full outer shell:

• metal atoms lose electrons to form positively charged ions
• non-metal atoms gain electrons to form negatively charged ions

Learn more on ionic bonding in this podcast.

Listen to the full series on BBC Sounds.

Open Transcript

Forming positive ions

Metal atoms lose electrons from their outer shell when they form ions:

• the ions are positive, because they have more protons than electrons
• the ions formed have full outer shells
• the ions have the electronic structure of a noble gas (group 0 element), with a full outer shell

For elements in groups 1, 2 and 3, the number of electrons lost is the same as the group number.

Forming negative ions

The outer shells of non-metal atoms gain electrons when they form ions:

• the ions formed are negative, because they have more electrons than protons
• the ions have the electronic structure of a noble gas (group 0 element), with a full outer shell

For elements in groups 6 and 7, the charge on the ion is equal to (8 minus group number).

Key factIons are formed by the transfer of electrons.

Example of ion charges and groups

Group	Element	Ion charge	Ion symbol
1	Na	+	Na+
2	Mg	2+	Mg2+
6	O	2-	O2-
7	Cl	-	Cl-

Group	1
Element	Na
Ion charge	+
Ion symbol	Na+

Group	2
Element	Mg
Ion charge	2+
Ion symbol	Mg2+

Group	6
Element	O
Ion charge	2-
Ion symbol	O2-

Group	7
Element	Cl
Ion charge	-
Ion symbol	Cl-

Example

Sulfur is in group 6 of the periodic table. What is the charge on its ions, and is the charge positive or negative?

The charge is negative, since sulfur is a non-metal. The charge on the ion is (8 - 6) = 2.

Question

Iodine is in group 7. What is the charge on its ions, and is the charge positive or negative?

Show answer

The charge is negative, since iodine is a non-metal. The charge on the ion is (8 - 7) = 1.

Next pageForming ionic bonds

More guides on this topic

• The three states of matter - AQA
• Interactive activity: Changes of state - AQA
• Small molecules - AQA
• Giant covalent molecules - AQA
• Metals and alloys - AQA
• Sample exam questions - bonding, structure and matter - AQA

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